US9602072B1 - Compact impedance tuner - Google Patents
Compact impedance tuner Download PDFInfo
- Publication number
- US9602072B1 US9602072B1 US14/751,544 US201514751544A US9602072B1 US 9602072 B1 US9602072 B1 US 9602072B1 US 201514751544 A US201514751544 A US 201514751544A US 9602072 B1 US9602072 B1 US 9602072B1
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- slabline
- disc
- probe
- center conductor
- tuner
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
- H03H7/38—Impedance-matching networks
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P5/00—Coupling devices of the waveguide type
- H01P5/04—Coupling devices of the waveguide type with variable factor of coupling
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
- H03H7/38—Impedance-matching networks
- H03H7/40—Automatic matching of load impedance to source impedance
Definitions
- This invention relates to RF load and source pull testing of low noise as well as medium and high power RF transistors and amplifiers using remotely controlled electro-mechanical impedance tuners.
- Load/source pull is a measurement technique employing microwave impedance tuners and other microwave test equipment ( FIG. 1 ), such as signal source ( 1 ), input and output tuner ( 2 , 4 ), power meter ( 5 ) and test fixture ( 3 ) which includes the DUT.
- the tuners and equipment are controlled by a computer ( 6 ) via digital cables ( 7 , 8 and 9 ).
- the microwave impedance tuners are devices which allow manipulating the RF impedance presented to the Device Under Test (DUT, or transistor) to test (see ref. 1); this document refers hence to “impedance tuners”, in order to make a clear distinction to “tuned receivers (radios)”, popularly called elsewhere also “tuners” because of the included tuning circuits (see ref. 2).
- Electro-mechanical impedance tuners in the microwave frequency range between 100 MHz and 60 GHz are using the slide-screw concept and include a slabline ( 24 ) with a test port and an idle port, a center conductor ( 23 ) (see also FIG. 3 ) and one or more mobile carriages ( 28 ) which carry a motor ( 20 ), a vertical axis ( 21 ) which controls the vertical position ( 216 ) of a reflective probe ( 22 ). The carriages are moved horizontally ( 217 ) by additional motors (not shown) and gear ( 27 ). The signal enters into one port ( 25 ) and exits from the other ( 26 ). In load pull the test port is the one where the signal enters, in source pull the test port is the one where the signal exits.
- the entire mechanism is, typically, integrated in a solid housing ( 215 ) since mechanical precision is of highest importance.
- FIG. 3 The typical configuration of the reflective probe inside the slabline is shown in FIG. 3 : a number of parallel reflective tuning elements ( 31 ) also called “tuning” probes or slugs, are inserted into the slotted transmission airline ( 34 ) and coupled capacitively with the center conductor to an adjustable degree, depending from very weak (when the probe is withdrawn) to very strong (when the probe is very close (within electric discharge—or Corona) to the center conductor; it must be pointed that capacitive “tuning” probes are different from “sampling” probes, which are loosely coupled with the center conductor; when the tuning probes move vertically ( 36 ) between a “top position” and a “bottom position” and approach the center conductor ( 33 ) of the slabline ( 34 ) and moved along the axis ( 35 ) of the slabline, they alter the amplitude and phase of the reflection factors seen at the slabline ports, covering parts or the totality of the Smith chart (the normalized reflection factor area).
- a typical value used for Zo is 50 Ohms (see ref. 3).
- Capacitive ground contact means extreme requirement in sidewall planarity and straightness to keep the quasi-sliding contact constant for the whole length and depth of the slabline as the probe moves into and along the slabline.
- Galvanic contact is safer, more repeatable and less vibration sensitive, but requires a spring mechanism to allow for constant pressure of the probe on the sidewalls.
- the probe of FIG. 4 a ) must have a springing mechanism ( 41 ) which is created by machining a horizontal hole ( 42 ) into the body of the probe.
- Probe 4 b ) can be massive ( 45 ).
- FIG. 1 depicts prior art, a typical automated transistor load pull test system.
- FIG. 2 depicts prior art, a front view of an automated slide screw impedance tuner using a single vertical axis and RF tuning probe (slug).
- FIG. 3 depicts prior art, RF probe (slug) inside a slotted airline (slabline) approaching the center conductor in a perspective view and the relevant dimensions and parameters of the operation.
- FIG. 4 depicts prior art, cross section of typical probe configurations: a) with galvanic ground contact to the slabline walls and spring mechanism; b) with capacitive RF ground contact.
- FIG. 5 depicts cross section A-B of circular tuner shown in FIGS. 6, 8 and 9 .
- FIG. 6 depicts top view of the circular tuner of FIG. 5 , showing the planetary movement of the disc-probe and tuning mechanism ( 2 rotations: arm rotation around the arm axis and probe rotation around the probe axis).
- FIG. 7 depicts top (a) and cross section (b) view of the disc-probe and its operation inside the circular slabline.
- FIG. 8 depicts a perspective view of the circular tuner.
- FIG. 9 depicts a perspective view of the circular tuner and the rotational movements of the carriage and the probe.
- FIG. 10 depicts a setup to calibrate a compact circular tuner.
- FIG. 11 depicts a calibration flowchart of circular impedance tuner.
- FIG. 12 depicts the comparative reflection behavior of disc probes versus prior art block probes as a function of probe penetration in the slabline.
- This invention discloses a new slide screw impedance tuner structure, the compact circular tuner. It comprises the following key components:
- the compact-circular tuner is approximately 1 ⁇ 3 long as a prior art linear tuner (compare FIGS. 2 and 8 and see ref. 2); table I summarizes this:
- the length reduction ratio increases as the frequency decreases, since the carriage width ( 220 ) and the width of connectors and sidewalls ( 215 ) in a linear tuner ( FIG. 2 ) are a fixed, frequency independent contribution to the overall length; the active section of horizontal travel of the tuner is one half of wavelength ( ⁇ /2) at the lowest operation frequency; this active section increases proportionally with decreasing lowest frequency.
- the connectors ( 604 ), ( 606 ) in FIG. 6 do not add to the overall length ( 607 ).
- the circular tuner ( FIGS. 5 and 6 , FIG. 5 shows a cross section of the top view of FIG. 6 ) comprises a slabline made of two conductive (preferably metallic) disc plates ( 55 , 57 ) and held together by a disc formed spacer ( 53 ); the center conductor is a toroid (circular rod) ( 56 ) which follows the periphery of the spacer ( 53 ) and is held in place by a number of supporting dielectric studs ( 52 ) distributed on the periphery of the spacer ( 53 ).
- a vertical axis ( 54 ) slides in the center of the bottom and top discs ( 55 , 57 ) and the spacer ( 53 ) and is attached on a mobile radial arm ( 59 ), which (optionally) carries also the motor control electronic board between both motors (shown in FIG. 10 as item ( 106 )); motor ( 58 ) is attached to the mobile arm ( 59 ) and rotates with it; at the end of the arm ( 59 ) sits a second motor ( 502 ) which carries on its axis ( 503 ) a metallic disc probe ( 50 ). Probe ( 50 ) is held eccentrically (see FIG.
- the arm ( 59 ) is supported by a rolling bearing ( 501 ) in order to maintain the vertical position of the probe ( 50 ) centered inside the slabline ( 55 , 57 ).
- the control mechanism for the amplitude of GAMMA is shown in detail in FIG. 7 : the rotation axis ( 74 ) of the disc probe ( 75 ) is placed eccentrically; the probe rotates around axis ( 74 ) whereby the geometrical center is at point ( 702 ); by rotating ( 73 ) the probe, using the motor ( 77 ) we control the coupling (distance between the bottom of the channel ( 78 ) and the center conductor) ( 72 ); this changes the amplitude of GAMMA between a minimum value close to 0 and a maximum value close to 1.
- typical eccentricity ( 701 ) must be at least of the order of 2 times the diameter of the center conductor ( 72 ).
- the rotation axis ( 74 ) is attached to an electric stepper motor ( 77 ), which controls the rotation angle ( 0 ) and the distance ( 703 ) between the bottom ( 78 ) of the disc-probe ( 70 ) and center conductor ( 72 ).
- the tuning resolution TR at the closest point ( 703 ) between probe bottom ( 78 ) and center conductor ( 72 ) is inversely proportional to the change in
- as a function of the change in angle ⁇ : TR 1/ ⁇
- FIG. 12 Typical reflection factor behavior of the basic types of tuning probes as a function of CONTROL is shown in FIG. 12 .
- Trace ( 120 ) corresponds to the rotating disc-probes used in the present circular tuner, whereas trace ( 121 ) corresponds to prior art cubical probes (slugs) which are used in linear, hitherto tuners ( FIGS. 3 and 4 ).
- the horizontal axis (GAMMA CONTROL) signifies the amount of coupling between the probe and the center conductor and is denominated generally as “Y”; for cubical probes in FIGS. 3 and 4 this signifies the distance [D] between the probe and the center conductor of the slabline, whereas in circular tuners with disc probes ( FIG.
- Tuning resolution is important for tuner accuracy, since, at high tuning resolution (which in our case corresponds to most useful range of maximum GAMMA) the effect of mechanical repeatability errors and loss of motor steps on tuning accuracy is strongly reduced. This means that small mechanical errors in probe angle positioning would cause negligible tuning errors. This is opposite, and much better, than in prior art tuners, where tuning resolution decreases at high GAMMA (see ref. 4).
- FIGS. 8 and 9 A perspective view of the circular tuner is shown in FIGS. 8 and 9 :
- Motors for phase control ( 85 ) and amplitude control ( 86 ) of GAMMA Motors for phase control ( 85 ) and amplitude control ( 86 ) of GAMMA; top ( 80 ) and bottom ( 81 ) plate of the slabline; center conductor ( 82 ); probe axis ( 87 ) and disc-probe ( 88 ), the probe comprises a center hole for practical reasons, in order to establish reliable sliding contact with the slabline walls; rotating arm ( 89 ) and input ( 83 ) and output ( 84 ) coaxial ports.
- FIG. 9 the rotation of the probe ( 91 ) and of the arm ( 92 ) are also shown.
- the tuner calibration process uses a setup as shown in FIG. 10 : the tuner is connected to a pre-calibrated vector network analyzer (VNA), ( 100 ) using high quality RF cables ( 103 , 104 ); the stepper motors ( 107 , 108 ) are directed by the control board ( 106 ), which communicates with the computer ( 102 ) to rotate the disc probes into the slot of the slabline in order to increase the GAMMA value, and the arm around the center of the slabline in order to adjust the phase, all while reading the four scattering parameters (s-parameters) from the VNA ( 100 ), using standard communication cable ( 101 ) and protocol.
- VNA vector network analyzer
- the reflection factor of the tuner at the test port is measured (for a source tuner test port is the signal exiting port, for a load tuner test port is the signal entry port) at typically 5 to 30 angle ⁇ values of the disc-probe, corresponding to minimum and maximum GAMMA (or S11), and saved in a scaling file in the form S11( ⁇ i, ⁇ o) ( 113 ); whereby ⁇ i is the relative angle of the probe rotation, starting with an initial position (zero), relative to the vertical direction ( FIG.
- ⁇ o is the arm rotation initialization angle (corresponding to “horizontal” zero; subsequently two-port s-parameters are measured ( 114 ) for combinations of both angles and saved in the form Sij( ⁇ i, ⁇ j); the horizontal position in linear tuner ( FIG.
- the measured data are then saved in a matrix [S] ( 115 ). This procedure is repeated for each frequency of interest and the data are saved for later use.
- Impedance synthesis using s-parameters of pre-calibrated tuners is a specific procedure related to specific tuners, which, in general terms, has been disclosed before (see ref. 6); this does not, however, limit the scope of the invention itself, since the invention relates to the new circular layout of the slabline and disc-probes used in the tuner apparatus rather than the tuning technique and presumes appropriate control software allowing calibration and tuning to be available.
- the calibration procedure has been laid out briefly only in order to manifest the fact that this wideband tuner is being used for impedance synthesis, when calibrated and the calibration data used accordingly.
- the computer When an impedance synthesis (tuning) is requested by a user, the computer loads the calibration data from memory (RAM or hard-disk) into its active memory and scans through the S11 data points to find the closest match between a calibrated reflection factor point and the requested GAMMA (or impedance). After this first step a second search is performed, in which interpolated data between calibration points are used (see ref. 4) and a final match is found, usually very close or identical to the requested value, within approximately 1% or better in reflection factor terms.
- 2 , whereby vector GAMMA
- These 3 sets of points are: point 1: ( ⁇ 1, ⁇ 1), ( ⁇ 1, ⁇ 2), ( ⁇ 1, ⁇ 3); point 2: ( ⁇ 2, ⁇ 1), ( ⁇ 2, ⁇ 2), ( ⁇ 2, ⁇ 3); and point 3: ( ⁇ 3, ⁇ 1), ( ⁇ 3, ⁇ 2), ( ⁇ 3, ⁇ 3).
- the ⁇ i and ⁇ j values are the angular coordinates of the closest calibrated points to the target reflection factor.
Abstract
Description
-
- 1. Load Pull Measurements, http://en.wikipedia.org/wiki/Load_pull
- 2. “Computer Controlled Microwave Tuner—CCMT”,
Product Note 41, Focus Microwaves, January 1998. - 3. Standing wave ratio, VSWR, https://en.wikipedia.org/wiki/Standing_wave_ratio
- 4. “High Resolution Tuners Eliminate Load Pull Performance Errors”, Application Note 15, Focus Microwaves, January 1995.
- 5. Anodization, http://en.wikipedia.org/wiki/Anodizing
- 6. TSIRONIS, U.S. patent application Ser. No. 12/929,643, “Method for Calibration and tuning using impedance tuners”
TABLE I |
Comparison total length of prior art and circular tuner |
Lowest | Prior art | New Circular | Length | ||
Frequency | Tuner | Tuner | reduction | ||
[MHz] | Length [cm] | Length [cm] | |
||
100 | 165 | 53 | 3.11 | ||
400 | 46.5 | 15.8 | 2.94 | ||
600 | 33.9 | 11.8 | 2.87 | ||
800 | 27.7 | 9.8 | 2.82 | ||
Sij(Φ,Ψk)=A(Φ)*Sij(Ψk,Φ1)+B(Φ)*Sij(Ψk,Φ2)+C(Φ)*Sij(Ψk,Φ3), (1)
Sij(Φ,Ψ)=A(Ψ)*Sij(Ψ1,Φ)+B(Ψ)*Sij(Ψ2,Φ)+C(Ψ)*Sij(Ψ3,Φ), (2)
whereby {i,j}={1, 2} and k={1, 2, 3}. The coefficients A, B, C are calculated using the following relations:
A(Θ)=(Θ−Θ2)*(Θ−Θ3)/((Θ1−Θ2)*(Θ1−Θ3)); (3)
B(Θ)=(Θ−Θ1)*(Θ−Θ3)/((Θ2−Θ1)*(Θ2−Θ3)); (4)
C(Θ)=(Θ−Θ2)*(Θ−Θ1)/((Θ3−Θ2)*(Θ3−Θ1)); (5)
whereby Θ is a generic variable that can be replaced, in equations (3) to (5), by Φ or Ψ accordingly; Ψ corresponds to the physical rotation angle of the mobile arm, and thus to the linear distance between the test port and the probe or the equivalent horizontal position of the probe in a prior art linear tuner, and Φ corresponds to the rotation of the disc probe and thus to the distance between the bottom of the probe groove and the center conductor inside the slabline, or the vertical position of prior art probes. These formulas allow calculating the s-parameters of the tuner using 3 sets of calibrated points (Ψi,Φj) with {i,j}={1, 2, 3}, surrounding the requested generic target position {Ψ,Φ} on the Smith chart. These 3 sets of points are: point 1: (Ψ1,Φ1), (Ψ1,Φ2), (Ψ1,Φ3); point 2: (Ψ2,Φ1), (Ψ2,Φ2), (Ψ2,Φ3); and point 3: (Ψ3,Φ1), (Ψ3,Φ2), (Ψ3,Φ3). The Ψi and Φj values are the angular coordinates of the closest calibrated points to the target reflection factor. The choice is adequate because a rotation of the arm (T) changes the distance of the probe and the carriage from the test port and thus the phase of the reflection factor and a rotation (Φ) of the disc-probe changes the gap between the probe and the center conductor and thus the amplitude of the reflection factor.
In particular the tuning procedure follows the following steps:
-
- i. The user defines the target impedance (GAMMA.target);
- ii. The search algorithm operates in computer memory and searches through the calibration data for the calibrated reflection factor value S11.c closest to GAMMA-target, for which the vector difference |S11.c-GAMMA.target| is smallest;
- iii. The probe rotation angle Φ, and arm rotation angle Ψ are changed alternatively using interpolated points, all in computer memory, in the vicinity of the calibrated point S11.c for S11 values closer than S11.c to GAMMA.target;
- iv. The arm angle Ψt and the probe angle Φt of the disc-probe corresponding to the closest found calibrated or interpolated point to GAMMA.target are determined;
- v. The mobile arm is rotated to the angle Ψt and the probe to the angle Φt, found in step (iv) to create the requested GAMMA.target.
Claims (8)
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Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9899984B1 (en) * | 2015-07-14 | 2018-02-20 | Christos Tsironis | Compact multi-carriage impedance tuner and method |
US10006951B1 (en) * | 2016-04-05 | 2018-06-26 | Christos Tsironis | Stable load pull operation using tuners |
US10693208B1 (en) | 2018-01-25 | 2020-06-23 | Christos Tsironis | High gamma disc-tuning probes for impedance tuners |
US11156656B1 (en) * | 2019-01-30 | 2021-10-26 | Christos Tsironis | Waveguide slide screw tuner with rotating disc probes |
US11402424B1 (en) * | 2019-10-03 | 2022-08-02 | Christos Tsironis | Low profile slide screw tuners and method |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8212629B1 (en) * | 2009-12-22 | 2012-07-03 | Christos Tsironis | Wideband low frequency impedance tuner |
US9257963B1 (en) * | 2013-06-27 | 2016-02-09 | Christos Tsironis | Impedance tuners with rotating probes |
US9276551B1 (en) * | 2013-07-03 | 2016-03-01 | Christos Tsironis | Impedance tuners with rotating multi-section probes |
-
2015
- 2015-06-26 US US14/751,544 patent/US9602072B1/en active Active
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8212629B1 (en) * | 2009-12-22 | 2012-07-03 | Christos Tsironis | Wideband low frequency impedance tuner |
US9257963B1 (en) * | 2013-06-27 | 2016-02-09 | Christos Tsironis | Impedance tuners with rotating probes |
US9276551B1 (en) * | 2013-07-03 | 2016-03-01 | Christos Tsironis | Impedance tuners with rotating multi-section probes |
Non-Patent Citations (1)
Title |
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Tsironis, U.S. Appl. No. 12/929,643, "Method for Calibration and tuning using impedance tuners". |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9899984B1 (en) * | 2015-07-14 | 2018-02-20 | Christos Tsironis | Compact multi-carriage impedance tuner and method |
US10006951B1 (en) * | 2016-04-05 | 2018-06-26 | Christos Tsironis | Stable load pull operation using tuners |
US10693208B1 (en) | 2018-01-25 | 2020-06-23 | Christos Tsironis | High gamma disc-tuning probes for impedance tuners |
US11156656B1 (en) * | 2019-01-30 | 2021-10-26 | Christos Tsironis | Waveguide slide screw tuner with rotating disc probes |
US11402424B1 (en) * | 2019-10-03 | 2022-08-02 | Christos Tsironis | Low profile slide screw tuners and method |
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